Composite sectionalized open-type drop-out-type fusible output with series enclosed current limiting fuse

ABSTRACT

A sectionalized open-type drop-out fusible cutout is provided having a high-current interrupting section, a mechanicallyconnected low-current interrupting section in electrical series therewith, the low-current section including a tensioned fuse and attached fuse-link cable, which, when fused, releasing the cable, effecting the breaking of the associated toggle linkage, and drop-out indicating action of the open-type fusible device. A high-current section includes a current-limiting fuse section, which is operative only during the interruption of heavy fault currents, and not operable during the interruption of relatively low overload currents, which overload currents are interrupted solely by the low-current section. The low-current section is of the expulsion type, having a fuse-link cable extending out through the lower open end of the fuse tube thereof, and maintaining the toggle linkage in its underset condition. The fusing of the low-current interrupting section, effects fusing of the fuse link and releases the fuse-link cable, and consequent breaking of the toggle linkage to permit consequent drop-out action of the open-type fusible cutout device. The aforesaid composite sectionalized open-type fusible device may be associated, with a load-break extension device, which will permit manual load breaking of load currents without either of the series fuse sections operating. Preferably, associated with the load-break device is an auxiliary arc-chute structure, serving to interrupt the load current within the arc-chute structure upon manual operation of the cutout device.

United States Patent [191 Cameron et al.

[111 3,827,010 July 30, 1974 [75] Inventors: Frank L. Cameron; John W.

Carothers, both of Irwin; Woodrow G. Shaw, Export, all of Pa.

[73] Assignee: Westinghouse Electric Corporation,

Pittsburgh, Pa.

22 Filed: Mar. 6, 1972 21 Appl. No.: 232,129

[52] US. Cl 337/168, 337/169, 337/171, 337/175 [51] Int. Cl. l-l0lh71/20 [58] Field of Search 337/168-179 [56] References Cited UNITEDSTATES PATENTS 2,230,955 2/1941 Johnson 337/170 2,441,692 5/1948 Earle337/237 X 2,483,577 10/1949 Fahnoe 337/161 3,235,688 2/1966 Fink ct a1337/156 3,377,447 4/1968 Hermann ct a1. 337/273 X Primary Examiner. l.D. Miller Assistant ExaminerFred E. Bell Attorney, Agent, or FirmW. R.Crout 57 ABSTRACT A sectionalized open-type drop-out fusible cutout isprovided having a high-current interrupting section, amechanically-connected low-current interrupting section in electricalseries therewith, the low-current section including a tensioned fuse andattached fuse-link cable, which, when fused, releasing the cable,effecting the breaking of the associated toggle linkage, and drop-outindicating action of the open-type fusible device.

A high-current section includes a current-limiting fuse section, whichis operative only during the interruption of heavy fault currents, andnot operable during the interruption of relatively low overloadcurrents, which overload currents are interrupted solely by thelow-current section. The low-current section is of the expulsion type,having a fuse-link cable extending out through the lower open end of thefuse tube thereof, and maintaining the toggle linkage in its undersetcondition. The fusing of the low-current interrupting section, effectsfusing of the fuse link and releases the fuse-link cable, and consequentbreaking of the toggle linkage to permit consequent drop-out action ofthe open-type fusible cutout device.

The aforesaid composite sectionalized open-type fusible device may beassociated, with a load-break extension device, which will permit manualload breaking of load currents without either of the series fusesections operating. Preferably, associated with the load-break device isan auxiliary arc-chute structure, serving to interrupt the load currentwithin the arc-chute structure upon manual operation of the cutoutdevice.

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COMPOSITE SECTIONALIZED OPEN-TYPE DROP-OUT-TYPE FUSIBLE OUTPUT WITHSERIES ENCLOSED CURRENT LIMITING FUSE CROSS-REFERENCE TO RELATEDAPPLICATIONS United States patent application, filed Aug. 26, 1970, Ser.No. 67,175, by Frank L. Cameron, and assigned to the assignee of theinstant application, teaches the use of a composite sectionalizedprotective indicating-type fuse structure having a high-currentinterrupting section and a mechanically-connected low-currentinterrupting section in electrical series therewith. The lowcurrentinterrupting section is replaceable, following a low-currentinterruption, which has no effect upon the high-current interruptingsection, the latter remaining intact, and may be further used. Duringhigh-current interruption, both sections are simultaneously fused, andcollectively contribute together to a quick interruption of theconnected electrical circuit, again there being an external indicatedcondition of the blown condition of the fuse by an ejection of thefuse-link cable.

Also, United States patent application, filed Aug. 26, 1970, Ser. No.67,183, by JamesN. Santilli, and likewise assigned to the assignee ofthe instant invention, shows a similar composite-type fuse structure, inwhich a high-current interrupting section and a low-current interruptingsection are utilized in series, the lowcurrent interrupting sectionbeing capable of being utilized' with a standard-type fuse-link.

BACKGROUND OF THE INVENTION Todays distribution systems are changing innumerous ways. There are to be found higher-density load areas, withattendanthigher-fault-current short-current capacities than existed inthe past. This is coupled with an increasing accent on safety, noisereduction, and convenience. In view of these new requirements, someformerly widely-used interruptingdevices and circuitprotective devicesare no longer fully suitable by todays standards. A case in point is thedistribution fuse cutout. These devices, while adequate for relativelyrural areas, havebeeen, and are used in large quantities to protectdistribution transformer circuits. The advantages of this type of deviceare its low cost, relative ease of refusing, and the widestandardization of fuse characteristics, which prevail. The device isless than desirable from the standpoint of limited interrupting rating aperformance that is characterized by loud noise, and the expulsion ofconsiderable are products, and its relatively unsafe performance in viewof the materials expelled. Maintenance men are subjected to this hazard.

SUMMARY OF THE INVENTION In accordance with a preferred embodiment ofthe present invention, there is provided a dual composite sectionalizedopen-type drop-out-type fusible cutout device, comprising a high-currentsection mechanically I connected and in electrical series with aseparable lowtion of relatively low currents (which have no effect uponthe high-current unit), and results in a drop-out indicative action ofthe associated toggle-linkage device, which thereby gives an indicatingreadily discernible visible view of the operated and blown condition ofthe device by the dropout action.

The low-current interrupting section preferably includes anexpulsion-type of fuse tube, which ejects the fuse link terminal and theassociated attached fuse link cable, releasing the toggle linkage duringfuse operation and thereby permits the assembly to drop to an externalobservable indicating position, and moreover permits ready drop-outaction of the fusible device.

The improved composite open-type sectionalized fusible device of thepresent invention may be utilized either with, or, optionally, withoutan auxiliary loadbreak extension device, as illustrated, and described,in part, in US. Pat. No. 3,235,688, issued Feb. 15, 1966,

to Austin J. Fink, Robert J. Lawrence, and Gene L. Miller, and assignedto the assignee of the instant application.

However, the improved composite open-type sectionalized fusible cutoutdevice of the present invention may be utilized, to advantage, even inthe absence of such a load-break extension device, and, in such aneventuality, utilized merely as a fusible protective device having thetwo series-related interrupting sections and having no manual load-breakcharacteristics.

It is, accordingly, a general object of the present invention to providean improved composite open-type sectionalized fusible cutout devicehaving indicative drop-out characteristics.

Another object of the present invention is to provide an improvedprotective open-type fusible device having high and low-currentinterrupting sections separably and detachably mechanically andelectrically connected together, so that replacement of the low-currentsection may easily take place without affecting the continued furtheruse of the high-current interrupting section.

Another object of the present invention is the provision of an improveddrop-out type fusible cutout device having interrupting capabilities farin excess of those attained heretofore.

Another object of the present invention is the provision of an improvedopen-type composite sectionalized fusible cutout device of the drop-outtype, which may be adapted both with, and without, an auxiliaryloadbreak extension device.

Still a further object of the present invention is the provision of animproved composite sectionalized drop-out fusible cutout device having acurrent-limiting fusible section associated therewith.

Another object of the present invention is the provision of an improveddrop-out type fusible cutout device having a high-currentcurrent-limiting section, and a serially-related low-currentexpulsion-type fuse-tube section having a fuse-link therein, capable,when fused, of actuating an associated toggle-linkage device to permitthereby quick drop-out action to an observable indicating position.

Still a further object of the present invention is the provision of animproved fusible device of the type set forth in theimmediately-preceding paragraph capable of being used with astandard-type fuse-link, such as k or T" links, for example, insertedinto the lowcurrent section, with the advantage of ready replacement andknown electrical characteristics.

Further objects and advantages will readily become apparent upon readingthe following specification, taken in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevational view of acomposite opentype sectionalized fusible cutout device embodying theprinciples of the present invention, and incorporating, as an optionaladdition, a manually-operable loadbreak extension device, the cutoutdevice being shown in the closed-circuit position;

FIG. 2 is a side elevational view of the composite fuse-holder assembly,only, with the auxiliary blade assembly, which is utilized inconjunction with the fusible device of FIG. 1, the fusible cutout devicebeing illustrated in its unfused intact condition;

FIG. 3 is a sectional view taken substantially along the line IIIIII ofFIG. 2;

FIG. 4 is a fragmentary vertical side elevational view takensubstantially along the line IV-IV of FIG. 2;

FIG. 5 is a top plan view of the composite fuse-holder assembly of FIG.2;

FIG. 6 is an enlarged side-elevational view, partially in section, ofthe high-current interrupting section, in this instance being of thecurrent-limiting type, the high-current section being illustrated in itsunfused intact condition;

FIG. 6A is an end view of the current-limiting fuse of FIG. 6;

FIG. 7 is a vertical sectional view taken through the low-currentinterrupting section, illustrated in this particular instance as of theexpulsion-fuse type.

FIG. 8 is a top plan view of the auxiliary interrupter with a portionbeing sectionalized to show the auxiliary contents;

FIG. 9 is a top plan view of the stationary latch for the main contact;

FIG. 10 is a front elevational view of the top casting;

FIG. 11 is a diagrammatic view illustrating the component parts of thecutout device, including the loadbreak attachment, the device beingindicated in the closed-circuit position;

FIG. 12 is a diagrammatic view, similar to that of FIG. 11, butillustrating the position of the parts during the initial portion of theopening operation, while the main contacts are open, and the auxiliarycontacts are still latched closed;

FIG. 13 is a diagrammatic view illustrating the fusible cutout devicewithout the optional load-break attachment, the device being illustratedin the closed circuit position;

FIGS. 14-18 are various views of the load-break mounting bracket;

FIGS. 19 and 20 are front and side elevational views of the spacerwasher used in the absence of the loadbreak mounting bracket of FIGS.14-18, when the load-break attachment is not desired;

FIG. 21 is an enlarged side elevational view of a standard-typefuse-link, with a portion of the fuse-tube casing broken away toillustrate the interiorly-disposed fusible link;

FIG. 22 illustrates the cutout device of FIG. 1 closed, with the loadcurrent being carried by the main contacts;

FIG. 23 illustrates the cutout device half open, with the quick-breakblade and arc-chute contact now carrying the load current;

FIG. 24 illustrates a further step in the opening operation, when thequick-break blade is beginning to be released, showing the main contactsof the cutout having been open sufficiently to prevent the are fromrestriking between the openedmain contacts;

FIG. 25 illustrates the quick-break blade having been released uponfurther opening movement of the cutout device, and illustrating how theblade snaps the full length of the arc-chute elongating and de-ionizingthe arc, with the coil spring at the bottom of the blade providing theopening energy thereof;

FIG. 26 illustrates the disposition of the load-break device during aclosing operation, when the blade is half closed with the main cutoutcontacts still disengaged, showing that the circuit is closed upon theloadbreak contacts, and not at the main contacts;

FIG. 27 is a side elevational view of the composite sectionalizedfuse-holder assembly, without the loadbreak attachment feature, thedevice being fragmentarily illustrated as in contact with the associatedstationary maincontact assembly supported by the upper end of theporcelain insulating support;

FIG. 28 is a fragmentary side-elevational view taken along the lineXXVIII-XXVIII of FIG. 27, illustrating the upper portion of thecomposite sectionalized fuse holder assembly of FIG. 8;

FIG. 29 is a top plan view of the upper end of the sectionalizedcomposite fuse-holder assembly of FIG. 27, taken substantially along theline XXIXXXIX of FIG. 27;

FIG. 30 is an elevational view of the fuse-link flipper, anddiagrammatically indicating the rotatable pivot therefor;

FIGS. 31-32 are detail views of the top contact bracket for thefuse-holder assembly,

FIGS. 33 and 34 are detail views of the auxiliarycontact biasing spring;and,

FIGS. 3537 are various views of the toggle-link hinge member, with FIG.37 being a partial sectional view taken along the line XXXVIIXXXVII ofFIG. 36.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Todays distribution systems arechanging in numerous ways. There are to be found higher density loadareas, with attendant higher fault current short-circuit capacities thanexisted in the past. This is coupled with an increasing accent onsafety, noise reduction and convenience. In view of these newrequirements, some formerly widely-used interrupting devices andcircuitprotective devices are no longer fully suitable by todaysstandards. A case in point is the distribution fuse cutout. Thesedevices, while adequate for relatively rural areas, have been and areused in large quantity to protect distribution transformer circuits. Theadvantage of this type of device is its low cost, relative ease ofrefusing, and the wide standardization of fuse characteristics whichprevail. The device is less than desirable from the standpoint oflimited interrupting rating, a performance that is characterized by loudnoise and the expulsion of considerable are products, and its relativelyunsafe performance in view of the materials expelled.

The present invention is particularly concerned with a new type ofdevice, which, in many instances, wil supplant the fuse cutouts andanswer, or overcome theobjectionable features associated generally withfuse cutouts. In more detail, the present invention may be called afused distribution limiter. The fused distribution limiter has a veryhigh fault-current interrupting rating, is still low in cost, operateswith a minimal noise and discharge, and yet retains time-currentcharacteristics, which do not depart from application patterns set inthe past. Especially desirable is the feature that the fuseddistribution limiter of the present invention can be used physicallyinterchangeably with the commonlyused distribution cutouts. The presentdevice of our invention will replace the same voltage of fuse cutout,and will fit into the same mounting, or fuse-support assembly as is usedfor the cutout. The device is further characterized by the feature thaton many conditions of fault interruption, thework of refusing andreplacement of the blown fuse-link is no more extensive than that whichis performed with the standard fuse cutout. Only in the event of veryhigh-fault currents does the improved and new current-limiting sectionof the device operate to give the characteristically higher interruptingrating and lower discharge associated with current-limiting fuses. Ourfuse distribution limiter may, optionally, be used for eitherload-break, or non-loadbreak applications by the simple expedient ofeasilymounted bolt-on parts. The constructional details of the improvedfuse distribution limiter of the present invention may be bestunderstood by reference to FIGS. 1-7 of the drawings, which illustratesthe improved composite sectionalized drop-out fusible device of thepresent invention, taken in conjunction with the readily attachableload-break extension device.

FIG. 1 illustrates the device in the closed-circuit position and isdesignated by the reference numeral 1. As shown, there is provided anupstanding insulating support 2, which has a centrally-disposedback-bracket 3, which may be bolted, or otherwise suitably secured tothe cross-arm (not shown) of a transmission-line pole. Disposed at theupper end of the insulating support 2 is an upper main stationarycontact assembly, generally designated by the reference numeral. 4.Also, associated with the lower end of the insulator support 2, andextending laterally therefrom, is a lower stationary main contactassembly 6.

Referring more particularly to the upper end of the interrupting device1, it will'be observed that the upper stationary main contactassembly 4includes a top casting 7 supporting the main stationary contactassembly, generally indicated at 4, and a secondary, or auxiliarycontact assembly, generally indicated at 9. The top casting 7 iscomprised of suitable conducting material, such as aluminum'bronze, forexample; and is secured to the insulator support 2 by any suitablemeans, such as by a bolt 10 extending through an aperture in the castingand an aperture extending through the insulator support 2. A nut, notshown, secures the bolt 10 to the insulator 2 and is accessible throughan aperture from the rear of the insulator support 2. The casting 7includes a curved rearwardly-extending portion 7a to mate with thecurvature of the insulator support 2, thus providing a snug fit.

A line-terminal clamp, generally indicated at 12, is associated with theconducting casting 7, and has a terminal bolt 10 extending through anaperture in the casting 7, as shown in FIG. 13. A clamp 17 is secured tocasting 7 by means of nut 18.

The main stationary contact assembly 4 includes a leaf contact member 20curved in a basically U-shaped configuration, and having a notch, orother opening, not shown, at one end for attachment by means of a bolt21 to an apertured contact mount 22 integral with, and protruding fromthe top casting 7. The stationary contact 20 may be comprised of anysuitable conducting material, such as phosphor bronze, for example.

A first contact latching device 24 is associated with the mainstationary contact 4, and is comprised of a basically U-shaped wire 25having leg portions 25a, 25b (FIG. 9) connected by a bight portion 250.The bight portion 25c is recurved to fit around the shank of bolt 21 foranchoring the first latching device 24 to the contact mount 22, as shownin FIG. 1. The outer ends of legs 25a, 25b are bent inwardly towardseach other, and are received in the ends of a metal tube 26, which tube26 serves as a contact-engaging member, as hereinafter described. v

The auxiliary contact assembly 9, shown in FIGS. 1 and 2, comprises asupport member 27 having a flat base 28 for attachment to the casting 7and an integral rib 29 (FIG. 8) on the base for supporting an auxiliarycontact assembly and an arc-chute. The support member 27 includes a pairof outwardly-extending studs 30, 31 foraffixing the base member to thetop casting 7 by means of a pair of bolts 32 (only one being shown)extending through apertures 33, 33 in the top casting 7 and into thestuds 30, 31.

A pair of auxiliary contact strips 34, 34 are mounted at opposite sidesof the rib 29 by means of a rivet 35 extending through the rib 29, andthe inner ends of the contacts 34, 34 as shown in FIG. 8. The outer ends340 of the contacts 34 are flared outwardly with respect to each other,to serve as a guide for the incoming auxiliary blade 36 to behereinafter described. Each contact blade 34 includes an integraltabular indentation 34b immediately adjacent the outer end 34a, eachindentation 34b extending inwardly toward the other substantially halfthe thickness of the rib 29, so that the indentations 34b normallytouch, thus comprising a second latching device, or stop 37, for theauxiliary blade 36, as hereinafter described. The contacts 34, 34 may beconstructed from any desirable conducting material, such as phosphorbronze, for example.

The arc-chute 39 is comprised of a pair of opposing arcing plates 41, 43fixedly mounted to the rib 29 by any suitable means, such as bolts 45,and attached to each other at various points around their perimeters bysuitable means, such as bolts 46. The arcing plates 41, 43 have theouter edge flared, as in FIG. 8, to provide a convergingentrance'portion 48 to the slot 49 between the plates 41, 43. The innersides of the plates 41, 43 are spaced from each other, except at the topand rear, where they are joined, to provide access for the auxiliaryblade 36. The plates 41, 43 are recessed,

as at 51 and 52, to provide space for the contacts 34.

Indentations 54, 54 areprovided in the interface of each plate 41, 43 toserve as a seat for compression springs 55, 55, each compressed betweenone of the indentations 54 and the indentation formed by thepreviously-described tabular stop 34b, 34b on the contacts 34, 34. It isseen that the tabular portion 34b on each blade 34 serves a dual purposein providing stop means for the auxiliary blade 36 and a spring seat forthe biasing springs 55. One of the plates 43 includes an integralinsulating hood 56 (FIG. 8) comprising a bottomless box extending overthe main contact assembly 4, and having cutout front and rear portions56a, 5612. Generally, the arc plates 41, 43 are comprised of a materialwhich is capable of evolving an arc-extinguishing gas when in theproximity to an electric arc. However, the present loadbreak fuse cutoutis of the open, or non-enclosed type intended for outdoor usage, andwhen so applied, the arc plates 41, 43 must be comprised of suitablematerial having acceptable arcquenching and weather-resistant abilities.

The use of highly-polymerized formaldehyde as an arc interrupter, isbroadly disclosed and claimed in US. Pat. No. 3,059,081, issued Oct. 16,1962 to Gordon C. Gainer and Albert P. Strom, and assigned to the sameassignee as the present application.

The lower stationary contact assembly 6 comprises a suitably-configuredhood plate 58 having a top wall portion 58a, side wall portions 58b, anda rear wall portion 580. The rear wall 58c is curved to mate withtheouter periphery of the insulator 2 and includes laterally-extendingapertured ear portions 58d, (only one shown) for connection to a bracket59 surrounding the insulator 2 and having studs 60 (only one shown)extending through the apertured ears 58d and secured thereto by nuts,61, 61.

A flexible stationary contact plate 63 is securedto the inside of therear wall by a suitable means, such as a rivet 64. The plate 63 may becomprised of any suitable conducting material, such as aluminum bronze,for example.

A line terminal clamp 66, similar to the previouslydescribed lineterminal clamp 17, is attached to the hood plate 58.

The hood 58 has provided on its side walls 58b means providing a hingepivot 67 for a composite fuse holder assembly to be hereinafterdescribed. More specifically, trunnion guide slots 68 are provided inthe side walls 58b of the hood 58, and have offset trunnion bearings, orseats 68a associated therewith.

The improved fusible device 1 of the present invention comprises twoserially-related fusible sections 70, 71, one section 70 being ahigh-current section and attached to a mechanically-connectedlow-current section 71, the two sections 70, 71 preferably beingremovably threaded, or otherwise detachably secured together, asindicated more clearly in FIG. 1 of the drawings. With reference to FIG.6 of the drawings, it will be observed that the high'currentinterrupting unit 70 generally comprises an enclosed cartridge device,or casing 72 at least partially filled with a granular material 73, suchas white sand, for example, and enclosing a fuse link 74 of silver, forexample, which extends from one end ferrule 76 to the other end ferrule77.

As shown in FIG. 6, the right end ferrule assembly 77 include a threadedsleeve 78, which accommodates, in threaded engagement, a slip nut 80having-a flange portion 80a, which abuts the upper end ferrule assembly82 of the lower low-current unit 71, which is preferably of theexpulsion-fuse type, and has a bore 84 therein for accommodation of afuse and a fuse-link cable, the latter being designated by the referencenumeral 86 in FIG. 1.

The low-current section 71, as more clearly illustrated in FIG. 7,comprises an insulating expulsion tube 87, having a plurality ofboric-acid blocks 88 stacked therein between a pair of end plugs 89 and90. The boric-acid blocks 88 evolve a condensible gas, including watervapor, during the heat of interruption, which occurs upon fusing of thefuse-link disposed within the bore 84 of the low-current section 71.

The expulsion section utilizes an interrupting medium of compressedboric acid, rather than the more commonly-used hard fibre, or Delrin.The use of boric acid in this section significantly reduces thedischarge occurring when the device operates to clear low-magnitudefault currents. At high values of fault current, that is currentmagnitudes higher than from 400 to 1,200 amperes, the current-limitingsection operates as well, so that the total discharge occurringcontinues at a reduced level.

Extending out the lower open end 84a of the expulsion fuse tube 87 isthe fuse-link cable 86. This cable extension is a portion of thefuse-link, generally designated by the reference numeral 85, andenclosed within the fuse tube 87, having at the upper end thereof afusible portion 85a, as well understood by those skilled in the art.

The lower end of the fuse-link cable extension 86 is secured by a wingbolt 91 to a toggle-link hinge mem ber 93, shown in detail in FIG. 2 ofthe drawings. Disposed adjacent the lower end of the fuse tube 87 is abottom clamping casting 95, shown in more detail in FIGS. 2 and 3. Theclamping casting 95 receives the fuse tube 87 therein, and is affixedthereto in any suitable manner, as by cement and being pinned at 95a. Apair of spaced integral leg portions 95b are provided on casting 95. Thelegs 95b are apertured at the outer ends to receive therethrough a shaft96, which shaft 96 is also received in suitably-apertured integral legmembers 97 on toggle link 93, thereby pivotally hinging the casting 95to toggle member 93, which together constitute a unitary toggleassembly, designated by the reference numeral 99.

The toggle member 93 is provided with an eyelet 100 enabling the prongof a switch stick to be inserted therein, so that the fuse-holderassembly 102 may be bodily lifted out of the trunnion bearings 68afollowing fuse operation and dropout action for a refusing operation.Also, the toggle-link hinge member 93 is provided with trunnions, orstub shafts 103, which cooperate with the trunnion bearings 68a of thelower hood 58. The base of each stub shaft 103 is provided with a cam104 having a narrow end 105. The cam provides maximum clearance forremoval and replacement of the fuse-holder assembly 102, and, by camaction reduces the side play of the fuse-holder assembly 102 in theslots 68 as the cutout'nears the closed position assuring that the maincontact and auxiliary blade will always be aligned for proper closingregardless of the angle of the closing force. A contact portion 107 onthe toggle member 93 cooperates with the flexible contact 63 to engagetherewith when the load-break fuse-cutout assembly 102 is in the closedposition, as illustrated in FIG. 1 of the drawings.

A fuse-link flipper 108 is rotatably mounted on a shaft 109 extendingbetween the legs 93a of the toggle hinge member 93. The flipper 108includes a pair of off-set leg members 108a having apertures at theirends surrounding the shaft 109, and having a bight portion 108!)connecting the legs 108a. The bight portion l08b carries an integrallatch portion 110 normally bearing against an integral catch 112 on thebottom of hinge casting 95. The latch 110 is normally held in engagementwith the catch 112 by the tension of fuse cable 86 against the bight108b, thus preventingdropout opera-' tion of the cutout 102, andreducing the strain on the fuse link 85, that would otherwise be exertedby the downward pressure of the'top contact 20 when latched. An integralspacer 114 on casting 95 abuts an integral stop-brace portion 116 tohold'casting 9 and toggle link 93 in under-toggle relationship. Thus,the top leaf contact member and the bottom flexible contact plate 63collectively constitute a toggle-link biasing means 11 acting to breakthe underset toggle linkage 118.

INTERCHANGEABILITY The novel fuse-holder assembly. 102 of the presentapplication is capable of use, optionally, with and without theload-break structure 122. The ferrule stud 124 at the upper end of thecurrent-limiting fuse 70 has a notch 124a provided therein, which is inalignment with the slot 78a provided in the lower ferrule sleeve 78, asillustrated in FIG. 1. If the device is to be used in conjunction withthe load-break attachment 122, as illustrated in FIG. 1, a hardwareitem, or load-break bracket 126, as illustrated in FIGS. 14-18, isslipped over the ferrule stud 124, so that the projection 126a (FIG; 15)fits within the recess 124a provided in the ferrule stud 124. The springsupport bolt 128 is then forced through the apertures 126b provided inthe downwardly-extending tabs 126a, as illustrated more clearly in FIG.16 of the drawings. A torsion spring 130 surrounds the spring-supportbolt 128 in a manner more clearly illustrated in FIG. 4 of the drawings.The rotatable auxiliary contact blade 36 has an aperture 36a providedthrough the lower portion thereof, which is pivotally mounted upon thetorsion-spring support bolt 128, the latter having a threaded endportion 128a, which accommodates a castellated nut 132, which is fixedlysecured upon the spring bolt 128 by a cotter pin 134. The rotatableauxiliary contact blade 36, in addition, has an offsetting boss portion36b, which engages one end of the torsion spring 130, and is biasedagainst the stop 126d, shown more clearly in FIG. 14 of the drawings.Thus, the rotatable auxiliary load-break contact blade 36 is pivotallymounted upon the springsupport bolt 128 to the bracket 126, and iscapable of being latched, so that it may move in the direction indicatedby the arrow 135 in FIG. 2, but not in the direction of the arrow 136indicated in FIG. 2, since it is prevented from so doing by the stopportion 126d, a part of the load-break bracket 126.

However, if the load-break disconnecting device 122 is not desired to beused in conjunction with the fuseholder assembly 102, then merelyasquare apertured spacer washer 137 is used in place of the load-breakbracket 126, as illustrated in FIGS. 19 and 20 of the drawings. I

Whether the load-break blade assembly 122 is used or not, the next itemto be assembled upon the ferrule stud 124 of the current-limiting fuse70 is the contactand-pry-out assembly bracket 138, as illustrated moreclearly in FIGS. 31 and 32. This will permit the latch 24 to be priedout by a downward pull exerted by a hook-stick upon the eyelet 139, asdescribed hereinafter.

The contact bracket 138 includes a movable main contact portion 142. Inaddition, it provides two spaced apertured ear portions 138a supportinga pin 143, about which encircles a torsion spring 144 biasing anunlatching mechanism assembly 145 in a clockwise direction, as viewed inFIGS. 2 and 27. The latch release lever 146 has an unlatching noseportion 147 which engages the latch 26 to effect opening motion of thefuseholder 102.

'Thus, in any event, the contact-and-pry-out bracket device 138 is usedwith the fuse-holder assembly 102, regardless of whether the load-breakbracket 126 and load-break blade 36 is used. As a final item upon thestud portion 124 is placed a washer 140, and, finally the locking nut141. Thus, depending upon whether the load-break bracket 126 is used thedevice 1 may be used with, or without the load-break attachment 122.FIGS. 2 and 27 illustrate the two forms of the invention.

A torsion flipper spring encircles shaft 109, thus constantly urging theflipper 108 in a counterclockwise direction around pivot shaft 109. Theflipper 108 also aids the fuse action in clearing faults by flipping thefuse cable 86 out of the fuse tube 87 during a fuse operation.

As shown, the manually-operable unlatching mechanism assembly, generallyindicated at 145, is carried by the ferrule stud 124 for unlatching thelatch 24 to effect load-break operation of the fuse cutout 1. Theunlatching assembly comprises the rotatable unlatching arm 146 aperturesat 146a to receive the pivot shaft 143. The shaft 143 extends through apair of spaced upstanding ears 138a, thus pivotally relating to theunlatching device 145 with the upper end of the currentlimiting fuse 70.The free end 147 of the unlatching arm'146 extends around the ferrule149 on top of contact portion 142 to normally rest beneath the latchtube 26 of latch 24, as seen in FIG. 1, when the switch 1 is in theclosed position. Integrallyformed with the unlatching arm 146 is anoperating ring, or eyelet 139 to render the unlatching device 145suitable for operation by the usual hookstick device. A hook-eye spring144 (FIG. 5) encircles the shaft 143 and has its end 144a bearingagainst the arm 146 to bias the unlatching device clockwise about pivot143 in the normally latched position, as shown in FIGS. 1 and 5. It isseen that the unlatching mechanism 145 and the latch 24, or first latchdevice, comprise a positive latching assembly, which prevents accidentalopening due to vibration or shock. The lineman must forceably pull downon eyelet 139 by his hookstick effecting thereby rotation of therotating arm 146 to release the latch 24.

As shown in FIG. 1, the load-break fuse cutout is in its normal closedposition with the main contact 142 latched into engagement with the mainline contact 20 by the first latching device 24. At the same time theauxiliary blade 36 is received between the contact strips 34 inwardly ofthe stop means, or second latching device 37. At the lower end of thefuse-holder 102, the casting 95 and toggle hinge 93 are held inunder-toggle relationship by the fuse-link cable 86 bearing upwardlyagainst flipper 108.

The load-break fuse cutout 1 may optionally operate either as a fusecutout, or as a loadbreak switch as has been described heretofore. Inthe operation of the loadbreak fuse cutout l as a fuse cutout, anoverload or fault current passing through the device will fuse thefusible section 85 (FIG. 21) whereupon the cable extension 86 willbecome slack, and will enable the flipper 108 to urge the cable 86downwardly out of the tube 87 as the flipper 108 rotatescounterclockwise under the urging of spring 120. Operation of theflipper 108 releases the latch 110 on flipper 108 from engagement withcatch 112 on casting 95, thereby permitting the fuse-holder assembly 102to drop downwardly and outwardly about the hinge pivot 68a to the fullyopen disconnected position (not shown). The downward movement of thefuse-holder 102 lowers contact 142 away from the first latching device24, thus effecting release of the main contact 142 with respect to themain stationarycontact 20. At the same time the auxiliary blade 36 iscarried downwardly between contacts 34, 34 and out of engagementtherewith during the initial downward movement of the fuse-holder 102,so that the fuse-holder 102 is thereafter allowed to'freely moveoutwardly around pivot 67, as previously de scribed.

The thickness of the blade 36 is slightly smaller than the spacingbetween the contacts 34, 34 to allow the blade 36 to easily drop out ofthe auxiliary contact assembly 9 during the above-described cutoutoperation, and also to minimize the contact between the blade 36 andcontacts 34, 34 when the cutout l is closed, whereby the major share ofthe current is carried through the main stationary contact assembly 4and main movable contact 142. I

In the operation of the load-break fuse cutout 1 as a load-break switch,the operating member 146, supported by the ferrule 149, is moveddownwardly and outwardly, the downward movement pivoting the unlatchingarm 147 upwardly about pivot 143 to engage the latch tube 26 and therebyrelease the first latching device 24 from engagement with contact 142,and the outward motion effecting rotation of fuse-holder 102 about thepivot 67 effecting disengagement between contact 142 and contact 20.During the initial outward movement of contact 142 away from contact 20,the auxiliary blade 36 is prevented from disengaging from contacts 34,34 by stop means or the second latching device 37 on contacts 34engaging blade 36. As the contact 142 moves further outwardly, the blade36 rotates about pivot bolt 128 (FIG. 4) on the load-break bracket 126,remaining for a time in engagement with contact stop or latching means34, 34 and carrying the full line current at this time to prevent arcingbetween the main contacts 142 and as they separate. The relativemovement between fuse-holder 102 and blade 36 will act to stress spring130 (FIG. 4). As the ferrule 149 moves further outwardly, blade 36slides downwardly over stop or latching means 34, 34 and, when the maincontacts 20, 142 have separated a sufficient distance to preventflashover, is completely withdrawn from between the contacts 34, 34 inthe downward direction,

whereupon spring 130 quickly moves the blade 36 out-.

wardly from the contacts 34, 34 in the opening direction and between thearc-plate means 41, 43 with a snap action out through the slot in theplates 41, 43 until the movable blade 36 is again substantially parallelwith the fuse-holder assembly 102 and in engagement with the stop means126d on arm 126. The movement of the rotatable blade 36 through the arcshute 39 will extinguish the are formed when the blade 36 disengagesfrom stationary auxiliary contacts 34, 34. As is generally known, thearc is extinguished by attenuation and confinement between the plates41, 43, and the gas blast produced by the gasevolving material, ashereinbefore described.

To close the load-break fuse cutout 1, the operating device 146 is movedinwardly by the maintenance man, rotating the fuse-holder 102 aboutbearing 67, effecting engagement of the auxiliary contact blade 34, 34before the main movable contact 142 engages main stationary contact 20.The stop means 126d on arm bracket 126 bears against rotatable blade 36during the closing operation effecting engagement with the contacts 34,34 before the main contacts 142 engage, and forcing the blade 36inwardly between guide members 34a, 34a and beyond stop means 34b to itsnormally closed position, as shown in FIG. 1. Upon the occurrence ofrelatively low-current faults, the standard fuse link 85 is fused andseparates to clear the circuit and to allow the toggle arrangement 99 tounlatch, dropping the fuse device 102 to the dropout lower position. Theexpulsion section utilizes an interrupting medium of compressed boricacid, rather than the more commonly-used hard fiber or Delrin. The

use of boric acid in this section 71 significantly reduces the dischargeoccurring when the fusible device 1 operates to clear low-magnitudefault currents. At high values of fault current, that is currentmagnitudes higher than 400 to 1,200 amperes, for example, thecurrentlimiting section operates as well, so that the total dischargeoccurring continues at a reduced level.

Thus, from the foregoing remarks, it is apparent that during relativelylow-fault current interruption, only the lower unit 71 operates, theupper unit 70 remaining intact, and merely replacement of astandard-type fuselink is required to convert the device again intooperating condition, and to again close the circuit through theconnected line. In the case of a relatively high fault current, both thehigh current and the low-current interrupting sections 70, 71 fusesimultaneously, and there is a reduced display since part of theinterrupting effort is accommodated in the enclosed high-currentinterrupting unit 70, such as the current-limiting section.

LOAD-BREAK OPERATION In electrical parallel with the top main contacts20 and 142 is another set of auxiliary contacts 34, and a quick-breakstainless steel blade 36 located between two pieces of insulating plate41, 43, composed, of Delrin, for example. The lineman inserts hishookstick in the fuse holder hook-eye 139, and pulls down in the usualmanner. First the main contacts 20 and 142 separate; however, current isstill carried through the quickbreak blade 36 until the main contacts20, 142 are far enough apart to prevent arcing. Second, the blade 36, bymeans of a strong spring action, then snaps away from its contact 34,drawing an are within the arc chute 39. A deionizing gas is generatedfrom the Deli-in" plastic when subjected to this are heat. The gas,combined with the snap action of the blade 36, quickly extinguishes theare thus completing a simple and safe load-break operation.

An important factor of this load-break operation in part lies in the arcchute 39, made of Delrin plastic, for example. This is a tough,temperature and moisture resistant material, which is highly suitablefor this purpose. The material cannot be ignited under load-breakconditions, due to the fast extinguishing action of the arc-chute. Thequick-break blade 36 is preferably made of stainless steel, for example.Pitting and erosion of the blade 36 after many operations, does notimpair the load-breaking ability of the cutout. An important advantageis that a conventional standard hookstick is the only tool needed toopen the cutout 1 under full load." Also, of important for the safety oflinemen is the fact that the are is completely confined within theDelrin arc-chute 39 with no chance of external arcing, as withfuse-link-break type of devices, nor is safety dependent uponreplacement of a gas capsule. In addition, under such load-breakoperations, no fuse-link need be replaced. Tests have clearly shown thatthe arc-chute 39 will interrupt 200 amperes over 200 times with theDelrin arc-chute 39 not tracking nor forming conducting carbonized pathsduring the entire life of the cutout.

FIG. 22 illustrates the cutout 1 closed with the load current beingcarried by the main contacts. FIG. 23 illustrates the cutout half openwith the quick-break blade 36 in the arc-chute now carrying the loadcurrent. FIG. 24 illustrates the quick -break blade 36 just before thereleasing action. It will be noted that the blade 36 cannot be releaseduntil the cutout is opened sufficiently to prevent the are fromrestriking between the main contacts 20, 142..

FIG. 25 illustrates the blade 36 released and further opening of thecutout releases the blade 36, and it snaps the length of the arc chuteelongating and deionizing the arc with the coil spring 130 at the bottomof the blade 36 providing the opening energy. FIG. 26 illustrates theblade half closed during a closing operation. This figure illustratesthat the cutouts main contacts 20, 142 engage after the quick-breakblade 36 closes, thus preventing burning and pitting due to prestrikingduring a closing operation.

The present device 1 is capable of use either with or without theload-break feature 122, as previously described. The foregoingdescription has described the load-break attachment 122; however, it isto be clearly understood that the device is capable of use without theload-break attachment 122, as illustrated in FIGS. 27, 28 and 29 of thedrawings. With respect to these figures, showing the use of the fusibledevice 1 without the load-break attachment 122, it is to be noted thatmany parts are similar in construction to the device, as describedhereinbefore.

By the use of the hook-stick, the latch releasing lever 146 may berotated about its pivot 143 to effect release of the latch 26 and permitopening motion of the fuseholder assembly 102.

It will be obvious to those skilled in the art that the current-limitingfusible section 70, illustrated in FIG. 6 of the drawings, couldbereplaced by other currentlimiting devices, such as those described inUS. Pat. No. 3,569,891 Cameron, issued Mar. 9, 1971. Merely, by way ofillustration only, has the particular type of current-limiting fusesection 70, illustrated in FIG. 6, been described in connection with thepresent invention. Alternates and different types of currentlimitingfuses could be substituted for that illustrated in FIG. 6. In addition,although boric acid blocks were described in conjunction with theexpulsion-type fusible device, illustrated in FIG. 7, other types ofexpulsion fuses could be utilized with the condition, however, that thefuse-link cable 86 therein would necessarily have to be severed toenable breaking of the toggle linkage 118.

From the foregoing description, it will be apparent that there has beenprovided an improved composite sectionalized dropout-type of fusibledevice 1, in which the noise and display has been minimized by utilizingtwo interrupting sections 70, 71 in series, one being a high-currentinterrupting section operable only during high-current interruption,whereas the other lowcurrent interrupting section 71 is operable bothduring low and high-current interruption Thus, the two sections 70, 71cooperate together to reduce the interrupting effort required by each.

To effect a fusing operation during low-current interruption, it ismerely necessary to unscrew the connecting slip ring 80 and to replacethe standard-type fuselink 85, illustrated more in detai in FIG. 21 ofthe drawings. Upon replacement of a standard fuse-link cable 86, thelow-current section 71 may again be mechanically attached to thehigh-current section by screwing the connecting slip ring 80 about thethreaded lower ferrule portion 78 of the upper high-current interruptingunit 70. The fuse-link cable 86 is then attached to the capstan device150, and the fuse structure 102 is then capable of being reinserted backinto the circuit.

From the foregoing description, it will be apparent that there has beenprovided an improved fusible device, particularly adapted for dropoutoperation, in which two fusible sections 70, 71 are arranged inelectrical series and adapted to be selectively fused. In other words,during low-current interruption, only the lower expulsion-type fusibledevice 71 functions, and the upper high-current unit remains intact.During high-current fault interruption, however, both sections 70, 71fuse simultaneously, thereby relieving each of them by their combinedaction, and the interrupting capability is increased with a concomitantlowering of noise and display. For load-break operation, merely by theexpedient of attaching additional hardware parts, theload-break-extension device 122 may be readily accommodated. On theother hand, should such a loadbreak function not be required, the device1 is fully capable of being operated independently thereof, and as acomposite two-sectioned fusible device, as illustrated in FIG. 27 of thedrawings. Also, from the foregoing description, it will be apparent thatthere has been provided a new circuitinterrupting device designed foruse with a standard fuse-support assembly, the device beingcharacterized by a higher and improved interrupting ability, achieved atthe same time with a reduced noise and display level. Moreover, thedevice is capable of being used with standard-type fuse-links, which maybe changed, depending upon thedesires of the maintenance man. Obviously,the fuse-links are of standard characteristics, and their level ofcurrent protection may be readily ascertained.

Although there has been illustrated and described specific structures,it is to be clearly understood that the same were merely for the purposeof illustration, and that changes and modifications may readily be madetherein by those skilled in the art, without departure from the spiritand scope of the invention.

What is claimed is:

1. A composite open-type drop-out fuse cutout comprising, incombination, means defining a pair of spaced line-contact assemblies, apivotally-mounted composite fuse-holder assembly including a togglelinkage and a fuse-tube assembly pivotally supported adjacent one endthereof to one of said line-contact assemblies, said compositefuse-holder assembly carrying a main movable contact adjacent the otherend thereof to make main contacting engagement with the otherline-contact assembly, means including a fuse-link extending throughsaid fuse-tube assembly for maintaining said toggle linkage in anunderset condition, means biasing said toggle linkage to a collapsedcondition, said fuse-tube assembly including an enclosed currentlimitingfuse-section disposed adjacent said other end of the compositefuse-holder assembly, said lowcurrent interrupting section accommodatingsaid fuselink, whereby on low-current interruption the lowcurrentsection only need be replaced in a re-fusing operation, and during heavyfault-current interruption both the low-current section and the enclosedcurrentlimiting fuse-section fusing, and the enclosure of thecurrent-limiting fuse-section preventing external emis sion of arcproducts.

2. The combination according to claim 1, wherein said compositeopen-type drop-out fuse cutout is adaptable for load-break operation,and delayed-acting load-break means having separable contacts andincluding a latching device is situated adjacent the free end of therotatable fuse-holder assembly, the separable contacts of saidload-break means being electrically in parallel with the circuitincluding said movable main contact and said one line-contact assembly.

3. The combination according to claim 2, wherein said load-break meansincludes a latching device, whereupon manual separation of said mainmovable contact from said other line-contact assembly will neverthelesscause continued latched contacting engagement of said delayed-actingload-break means for a predetermined time.

4. The combination according to claim 2, wherein said load-break meansis responsive to the collapse of said toggle linkage duringfault-current interruption to effect release of said latching device,whereby during fault-current interruption the fuse-holder assembly mayfreely rotate about said one line-contact assembly to an open indicatingobservable position.

5. The combination according to claim 1, wherein the low-currentinterrupting section is an expulsiontype interrupting section andincludes a standard-type fuse-link.

6. The combination according to claim 1, wherein a readily detachablemeans interconnects mechanically the enclosed current-limiting fusesection and the lowcurrent interrupting section.

7. The combination according to claim 1, wherein a flipper exertstension force upon the fuse-link cable, and biasing means is associatedwith said flipper to create said force tension.

8. The combination according to claim 2, wherein the load-break meansincludes an arc-chute structure including a pair of closely-spacedinsulating plates.

9. The combination according to claim 8, wherein said closely-spacedinsulating plates evolve an arcextinguishing gas.

10. The combination according to claim 1, wherein the free end of thefuse-holder assembly is capable of readily adapting attaching parts toadapt it to a loadbreak device.

11. The combination according to claim 1, wherein tube having aplurality of apertured gas-evolving blocks stacked therein.

12. The combination according to claim 11, wherein said apertured blocksare of boric acid.

13. The combination according to claim 1, wherein only a single fuseelement is employed in the enclosed current-limiting fuse section.

14. A composite fuse-holder assembly including an enclosedcurrent-limiting section and a serially-related low-current interruptingsection, toggle means clamped to one end of said composite fuse-holderassembly, said toggle-means comprising a toggle-leg member fixedlyclamped toone end of the fuse-holder assembly, a toggle-linkhinge-member pivotally connected to said toggle-link member so as toform a toggle-linkage therewith, a fuse-link having a fuse-link cabledisposed interiorly of said fuse-holder assembly and having one end ofthe fuse-link cable extending out of one end of the compositefuse-holder assembly and removably attached to said toggle-linkhinge-member, whereby said toggle-means is maintained in an undersetcondition, said toggle-link hinge-member having a pair oflaterally-extending trunnion-bearings so as to make said compositefuse-holder assembly adaptable for insertion into a conventional-typeopen-style fuse mounting, said fuse-holder assembly including anenclosed currentlimiting fuse-section disposed adjacent the other end ofsaid composite fuse-holder assembly, the device functioning duringlow-current interruption to cause only fusing of the low-current sectionand no fusing of the current-limiting fuse-section, and said devicefurther functioning on heavy fault-current interruption for both fusesections to fuse with the enclosed housing of the current-limiting fusesection preventing the emission of hot arc gas products externally ofthe device.

15. The combination of claim 14, wherein the lowcurrent interruptingsection is an expulsion-type fuse device having the upper end closed andcausing the ejection of fuse products out of the lower open end of theexpulsion-type fuse.

16. The combination according to claim 14, wherein the enclosedcurrent-limiting section and the lowcurrent interrupting section aremechanically separable.

17. The combination of claim 14, wherein the lowcurrent interruptingsection accommodates a standardtype fuse-link available in variantratings and interchangeable within the low-current interrupting section.

18. The combination according to claim 14, wherein the fuse-holderassembly has an auxiliary contact-blade rotatably mounted adjacent theupper free end of the fuse-holder assembly.

19. The combination according to claim 18, wherein the auxiliarycontact-blade is biased in the direction of opening drop-out motion ofthe composite-type fuseholder assembly.

20. The combination according to claim 14, wherein an optionalload-break device including a rotatable auxiliary contact-blade may beattached adjacent the free end of the composite-type fuse-holderassembly at the option of the user.

21. The combination according to claim 16, wherein the detachableconnection includes a rotatable sleeve having a threaded connection toone of the fuse sections.

. said blocks are of boric acid.

26. An open-type drop-out type fusible cutout including meansinsulatingly supporting in spaced relation a pair of main-line contacts,a hinge-support asso ciated with one of said main-line contacts, arotatable fuse-holder assembly adapted for pivotable mounting about saidone hinge-support and including in series relationship an enclosedcurrent-limiting fuse-section and a serially-related low-currentinterrupting section of the expulsion-fuse type, said rotatablefuse-holder assembly having a movable main contact adjacent its outerfree end, and load-break means carried partially by the outer free endof the rotatable fuse-holder assembly and also by said otherline-terminal assembly, said load-break means including a quick-breakauxiliary contact-blade, and an arc-chute with the arc-chute enclosing acooperable auxiliary contact.

1. A composite open-type drop-out fuse cutout comprising, incombination, means defining a pair of spaced line-contact assemblies, apivotally-mounted composite fuse-holder assembly including a togglelinkage and a fuse-tube assembly pivotally supported adjacent one endthereof to one of said line-contact assemblies, said compositefuse-holder assembly carrying a main movable contact adjacent the otherend thereof to make main contacting engagement with the otherline-contact assembly, means including a fuse-link extending throughsaid fuse-tube assembly for maintaining said toggle linkage in anunderset condition, means biasing said toggle linkage to a collapsedcondition, said fuse-tube assembly including an enclosedcurrent-limiting fusesection disposed adjacent said other end of thecomposite fuseholder assembly, said low-current interrupting sectionaccommodating said fuse-link, whereby on low-current interruption thelow-current section only need be replaced in a re-fusing operation, andduring heavy fault-current interruption both the low-current section andthe enclosed current-limiting fusesection fusing, and the enclosure ofthe current-limiting fusesection preventing external emission of arcproducts.
 2. The combination according to claim 1, wherein saidcomposite open-type drop-out fuse cutout is adaptable for load-breakoperation, and delayed-acting load-break means having separable contactsand including a latching device is situated adjacent the free end of therotatable fuse-holder assembly, the separable contacts of saidload-break means being electrically in parallel with the circuitincluding said movable main contact and said one line-contact assembly.3. The combination according to claim 2, wherein said load-break meansincludes a latching device, whereupon manual separation of said mainmovable contact from said other line-contact assembly will neverthelesscause continued latched contacting engagement of said delayed-actingload-break means for a predetermined time.
 4. The combination accordingto claim 2, whereiN said load-break means is responsive to the collapseof said toggle linkage during fault-current interruption to effectrelease of said latching device, whereby during fault-currentinterruption the fuse-holder assembly may freely rotate about said oneline-contact assembly to an open indicating observable position.
 5. Thecombination according to claim 1, wherein the low-current interruptingsection is an expulsion-type interrupting section and includes astandard-type fuse-link.
 6. The combination according to claim 1,wherein a readily detachable means interconnects mechanically theenclosed current-limiting fuse section and the low-current interruptingsection.
 7. The combination according to claim 1, wherein a flipperexerts tension force upon the fuse-link cable, and biasing means isassociated with said flipper to create said force tension.
 8. Thecombination according to claim 2, wherein the load-break means includesan arc-chute structure including a pair of closely-spaced insulatingplates.
 9. The combination according to claim 8, wherein saidclosely-spaced insulating plates evolve an arc-extinguishing gas. 10.The combination according to claim 1, wherein the free end of thefuse-holder assembly is capable of readily adapting attaching parts toadapt it to a load-break device.
 11. The combination according to claim1, wherein the low-current section includes an expulsion-type fuse tubehaving a plurality of apertured gas-evolving blocks stacked therein. 12.The combination according to claim 11, wherein said apertured blocks areof boric acid.
 13. The combination according to claim 1, wherein only asingle fuse element is employed in the enclosed current-limiting fusesection.
 14. A composite fuse-holder assembly including an enclosedcurrent-limiting section and a serially-related low-current interruptingsection, toggle means clamped to one end of said composite fuse-holderassembly, said toggle-means comprising a toggle-leg member fixedlyclamped to one end of the fuse-holder assembly, a toggle-linkhinge-member pivotally connected to said toggle-link member so as toform a toggle-linkage therewith, a fuse-link having a fuse-link cabledisposed interiorly of said fuse-holder assembly and having one end ofthe fuse-link cable extending out of one end of the compositefuse-holder assembly and removably attached to said toggle-linkhinge-member, whereby said toggle-means is maintained in an undersetcondition, said toggle-link hinge-member having a pair oflaterally-extending trunnion-bearings so as to make said compositefuse-holder assembly adaptable for insertion into a conventional-typeopen-style fuse mounting, said fuse-holder assembly including anenclosed current-limiting fuse-section disposed adjacent the other endof said composite fuse-holder assembly, the device functioning duringlow-current interruption to cause only fusing of the low-current sectionand no fusing of the current-limiting fuse-section, and said devicefurther functioning on heavy fault-current interruption for both fusesections to fuse with the enclosed housing of the current-limiting fusesection preventing the emission of hot arc gas products externally ofthe device.
 15. The combination of claim 14, wherein the low-currentinterrupting section is an expulsion-type fuse device having the upperend closed and causing the ejection of fuse products out of the loweropen end of the expulsion-type fuse.
 16. The combination according toclaim 14, wherein the enclosed current-limiting section and thelow-current interrupting section are mechanically separable.
 17. Thecombination of claim 14, wherein the low-current interrupting sectionaccommodates a standard-type fuse-link available in variant ratings andinterchangeable within the low-current interrupting section.
 18. Thecombination according to claim 14, wherein the fuse-holder assembly hasan auxiliary contact-blade rotatably mounted adjacent the upper free endof the fuse-holder asSembly.
 19. The combination according to claim 18,wherein the auxiliary contact-blade is biased in the direction ofopening drop-out motion of the composite-type fuse-holder assembly. 20.The combination according to claim 14, wherein an optional load-breakdevice including a rotatable auxiliary contact-blade may be attachedadjacent the free end of the composite-type fuse-holder assembly at theoption of the user.
 21. The combination according to claim 16, whereinthe detachable connection includes a rotatable sleeve having a threadedconnection to one of the fuse sections.
 22. The combination according toclaim 14, wherein a spring-biased fuse-link flipper maintains tensionupon the fuse-link cable.
 23. The combination according to claim 22,wherein the toggle link member has a shoulder portion and the fuse-linkflipper latches under said shoulder to somewhat relieve thetension-pressure upon said fuse-link cable.
 24. The combinationaccording to claim 14, wherein the low-current section includes aplurality of apertured gas-evolving blocks.
 25. The combinationaccording to claim 24, wherein said blocks are of boric acid.
 26. Anopen-type drop-out type fusible cutout including means insulatinglysupporting in spaced relation a pair of main-line contacts, ahinge-support associated with one of said main-line contacts, arotatable fuse-holder assembly adapted for pivotable mounting about saidone hinge-support and including in series relationship an enclosedcurrent-limiting fuse-section and a serially-related low-currentinterrupting section of the expulsion-fuse type, said rotatablefuse-holder assembly having a movable main contact adjacent its outerfree end, and load-break means carried partially by the outer free endof the rotatable fuse-holder assembly and also by said otherline-terminal assembly, said load-break means including a quick-breakauxiliary contact-blade, and an arc-chute with the arc-chute enclosing acooperable auxiliary contact.